lkml.org 
[lkml]   [2012]   [Aug]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 0/4] promote zcache from staging
On 08/17/2012 05:21 PM, Dan Magenheimer wrote:
>> From: Seth Jennings [mailto:sjenning@linux.vnet.ibm.com]
>> Subject: Re: [PATCH 0/4] promote zcache from staging
>>
>> On 08/09/2012 03:20 PM, Dan Magenheimer wrote
>>> I also wonder if you have anything else unusual in your
>>> test setup, such as a fast swap disk (mine is a partition
>>> on the same rotating disk as source and target of the kernel build,
>>> the default install for a RHEL6 system)?
>>
>> I'm using a normal SATA HDD with two partitions, one for
>> swap and the other an ext3 filesystem with the kernel source.
>>
>>> Or have you disabled cleancache?
>>
>> Yes, I _did_ disable cleancache. I could see where having
>> cleancache enabled could explain the difference in results.
>
> Sorry to beat a dead horse, but I meant to report this
> earlier in the week and got tied up by other things.
>
> I finally got my test scaffold set up earlier this week
> to try to reproduce my "bad" numbers with the RHEL6-ish
> config file.
>
> I found that with "make -j28" and "make -j32" I experienced
> __DATA CORRUPTION__. This was repeatable.

I actually hit this for the first time a few hours ago when
I was running performance for your rewrite. I didn't know
what to make of it yet. The 24-thread kernel build failed
when both frontswap and cleancache were enabled.

> The type of error led me to believe that the problem was
> due to concurrency of cleancache reclaim. I did not try
> with cleancache disabled to prove/support this theory
> but it is consistent with the fact that you (Seth) have not
> seen a similar problem and has disabled cleancache.
>
> While this problem is most likely in my code and I am
> suitably chagrined, it re-emphasizes the fact that
> the current zcache in staging is 20-month old "demo"
> code. The proposed new zcache codebase handles concurrency
> much more effectively.

I imagine this can be solved without rewriting the entire
codebase. If your new code contains a fix for this, can we
just pull it as a single patch?

Seth



\
 
 \ /
  Last update: 2012-08-18 02:41    [W:0.266 / U:0.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site